Area codes in Boulder, Colorado
Boulder, Colorado uses 3 area codes — 303, 720 and 983. The main Boulder area code is 303.
Area codes serving Boulder
Phone numbers in Boulder are written as ten digits — for example (303) 555-0190 — and fall in the Mountain Time zone.
How Boulder came to have 3 area codes
The original Boulder area code is 303, in service since 1947. As the area ran low on available numbers, overlay codes were added over the same region for new phone lines: 720 (1998) and 983 (2022). Existing numbers kept their original code — an overlay never forces anyone to change their number — which is why Boulder now uses all 3 codes and every local call is dialed with ten digits.
All Colorado area codes · Is a Boulder call a scam?
Nearby cities
- Longmont area codes
- Westminster area codes
- Denver area codes
- Brighton area codes
- Loveland area codes
- Lakewood area codes
- Aurora area codes
- Littleton area codes
More cities in Colorado
Frequently asked questions
What is the area code for Boulder?
The main area code for Boulder, Colorado is 303. Boulder is now served by 3 area codes in total: 303, 720, 983.
How many area codes does Boulder have?
Boulder has 3 area codes: 303, 720, 983.
Why does Boulder have more than one area code?
As Boulder used up the numbers available in its original area code (303, in service since 1947), additional "overlay" codes were added over the same area so new phone numbers could keep being assigned.
How do you dial a Boulder number?
Dial all 10 digits — the area code (303 or 720 or 983) followed by the 7-digit local number. From abroad, dial +1, then the area code and number.
Sourced from the official NANPA (North American Numbering Plan Administrator) numbering database, current as of August 2, 2026. Refreshed monthly.